LTC1921 - Dual -48V Supply and Fuse Monitor

The LTC®1921 monitors two independent –48V supplies, including their fuses, and drives up to three optoisolators to indicate status, in accordance with standard backplane specifications. Requiring only three noncritical resistors and optoisolators, the LTC1921 replaces multiple voltage comparators, a voltage reference and several precision resistors.

The monitor features dual supply overvoltage and undervoltage detection circuits. The preset trip thresholds include overvoltage, undervoltage and undervoltage recovery that are guaranteed over temperature and meet or exceed common backplane specifications. Additional built-in circuitry detects the condition of supply fuses. Overvoltage and undervoltage detectors ignore fast supply transients, eliminating false detection. The LTC1921 operates from –10V to –80V with a typical power dissipation of less than 10mW.

The LTC1921 is available in 8-pin MSOP and SOIC packages.

  • Withstands Transient Voltages Up to 200V/–200V
  • Requires No Precision External Components
  • Independently Monitors Two –48V Supplies for
  • – Undervoltage Faults: –38.5V ±1VMAX – Overvoltage Faults: –70V ±1.5VMAX
  • Accurately Detects Undervoltage Fault Recovery: –43V ±0.5VMAX
  • Monitors Two External Fuses
  • Operates from –10V to –80V
  • Tolerates DC Faults to –100V
  • Tolerates Accidental Supply Reversal to 100V
  • Small Footprint: 8-Lead MSOP Package
  • Specified from –40°C to 85°C
Typical Application
LTC1921 Typical Application
  • Telecom Backplanes or Switch Cards
  • Networking Backplanes or Switch Cards
  • High Voltage Fuse Monitoring
LTC1921 Package Drawing
LTC1921 Package Drawing
Order Information
Part NumberPackageTempPrice(1-99)Price (1k)*
Demo Boards
Part NumberDescriptionPrice
DC548ALTC1921CMS8 | Dual -48V Suppy and Fuse MonitorContact Factory
Design Note
Reliability Data
LT Journal
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LTC1921 - Dual -48V Supply and Fuse Monitor
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R413 Reliability Data
Aug 2002 Simplify Telecom Power Supply Monitoring with the LTC1921 Integrated Dual -48V Supply and Fuse Monitor
Dec 2003 Single IC Monitors Redundant -48V Supplies and Fuses without Precision External Components
November 2004 - -48V Backplane Impedance Analyzer Takes the Guesswork Out of Sizing Clippers and Snubbers
LTC1921 Footprints and Symbols